Presbyopia

The need for near vision lenses is almost universal for people
as they enter their middle years. As we mature, the natural crystalline lenses in our eyes become firm, enlarged, and
will
lose flexibility. This naturally occurring event will decrease
the ability of the crystalline lens to vary its shape for different
ranges of focus. This condition is known as presbyopia and is most
often first detected in people between 40 and 50 years of age. A
sure sign of presbyopia is when you cannot read without holding
the item far away from you. For many, distance vision remains relatively
unaffected by presbyopia.

Bifocals, Trifocals, Reading Glasses

When presbyopia occurs, most people do well with reading glasses,
bifocals, or trifocal lenses. Reading glasses, bifocals, and trifocals
are plus-powered lenses that would normally be used for someone
who has hyperopia (farsighted, longsighted), however a plus-powered
lens helps someone who is presbyopic because these lenses provide
a small amount of myopic (nearsighted, shortsighted) vision.

There are two ways to describe myopia. One is that you cannot
see things far away very well. The other is that you can see things
close very well. People with a small amount of myopia can simply
remove their glasses to read. However, people with previously normal
vision, those already hyperopic, or those who wear contact lenses
with full distance correction may need to use reading glasses for
close work.

Even if not currently having problems with presbyopia, if contemplating
refractive surgery and near age 40, after correction with refractive
surgery a person may be hit with the immediate need for reading
glasses due to a phenomenon we call "Sudden
Presbyopia".

Bifocals and trifocals are used to provide both near and far
vision without having to constantly put on and take off a pair of
glasses or switch between two pairs of glasses.

Cannot Be Nearsighted and Farsighted

Because reading glasses provide a plus power that would normally
be used to correct hyperopia, many people incorrectly believe they
are becoming hyperopic. Those previously myopic may believe they
are both hyperopic and myopic, which are mutually exclusive. Whenever
changes in vision occur, it is always best to be evaluated by a
competent eye care physician to determine the problem exactly.

Anyone who has needed to use readers, as they are often called,
knows just how frustrating and irritating presbyopia can be. Many
people have had excellent near and distant vision without glasses
all their lives, until those dreaded readers become necessary because
of presbyopia.

Reliable Workaround

There are currently no reliable and predictable surgery techniques
or medications that will outright cure presbyopia, however there
are a number of permanent and semi-permanent techniques to deal
with the focusing changes and challenges caused by presbyopia. One
of the more popular ways to work around presbyopia is with monovision
correction. For many, monovision will reduce or eliminate the need
for readers, bifocals, or trifocals. The concept of monovision is
very simple. One eye is corrected for near vision and the other
eye is corrected for distance vision. The brain figures out which
eye to use and when. How to achieve monovision varies, depending
upon the patient's current eyesight.

If a person has never needed corrective lenses like glasses or
contacts before, then a small amount of myopia can be induced in
that person's non-dominant eye. The dominant eye remains uncorrected, as it already provides full
distance vision. Download the USAEyes Dominant Eye Test and check which eye is dominant
now.

If a person already has less than two diopters of myopia, that person's dominant eye can be fully
corrected for distance vision, and the non-dominant eye not changed,
which already provides good near vision.

People with greater amounts of myopia may have the dominant eye
fully corrected to provide good distance vision, and the non-dominant
eye undercorrected to less than two diopters myopic for good near
vision. A patient who is already hyperopic may have the non-dominant
eye overcorrected into myopia, plus the dominant eye either corrected
for distance vision or untouched.

Contacts or Surgery

Monovision can be achieved through contact lenses or through refractive surgery. NearVision
CK has been specifically approved by the FDA for monovision correction and is most ideal for patients
who are mildly hyperopic or are plano and have never needed glasses. NearVision CK uses radio waves to
change the shape of the cornea and create a small amount of myopia
in the non-dominant eye. This myopia provides near vision, while
the other uncorrected eye provides distance vision. NearVision CK
is considered temporary because the effect does diminish with time,
however the regression of the NearVision CK effect is very slow
and can last for years.

Although not specifically approved by the FDA for monovision,
the use of Lasik, LASEK, PRK, and Epi-Lasik are also appropriate techniques to create monovision as an off label use of the excimer laser.

The chief advantage of monovision is the freedom it can provide
from reading glasses. After six to eight weeks the brain makes the
vision changes automatically, without any conscious effort or awareness.
Monovision makes it possible to repeatedly change the range of focus,
without having to constantly remove or add corrective lenses.

Monovision Drawbacks

As with many good things, monovision comes with some disadvantages.
People with monovision may have some degree of decreased depth perception unless corrective lenses are used to fully
correct the slightly myopic eye. They may also notice blurred vision
in the "near" eye when glancing in the side mirror of their cars
or when the vision in the "distance" eye is blocked by an object.

We highly recommend someone with monovision have a pair of glasses
made that provide full distance vision correction for those situations
where excellent distance vision and/or depth perception are desirable.
For detail activities such as prolonged reading, have a pair of
reading glasses made that provide balanced near vision. It may be
possible to purchase an identical pair of readers with two different
powers of correction, and switch lenses to provide the balance to
full near correction with both monovision eyes.

Test In Contacts First

If monovision seems desirable, you should try to achieve the
effect with contact lenses prior to surgery to determine if monovision
is suitable for your individual needs and your ability to adapt.
Should you initially choose surgical monovision and subsequently
become unhappy with it, enhancement
surgery to fully correct the undercorrected eye and reverse
the monovision effect is often an option.

People who are entering mid-life and are interested in monovision
should discuss the matter with their doctor prior to undergoing
surgery. It is surprising how many patients adapt readily and happily
to this vision option, however monovision is not for everybody and
some people dislike its effect.